This isn't critical in the sense of security issues, but it's critical as in, a crucial basic phone feature is crippled. Seemingly at random times, when people call me, the phone only rings twice, then it's silent the rest of the way during their call attempt. Someone on another forum said they figured out it was happening with any ring tones shorter than 5 seconds... but this includes even the built-in iPhone ring tones! If you Google around, you'll find lots of people having this issue (it might be specific to 3GS?). I doubt it's a hardware issue though. I SERIOUSLY hope this is in the 3.1 update coming in the next month or two.